Domino effect of climate events could lead to irreversible “hothouse Earth” state

28. August 2018

Professor Katherine Richardson from the DNRF Center for Macroecology, Evolution and Climate (CMEC) is part of a research team warning that an uncontrollable domino effect is likely to dramatically exacerbate global warming. The researchers point out that the goal of the Paris Agreement is probably not enough to avoid this development.

(The map shows potential tipping cascades. The individual tipping elements are color-coded according to estimated thresholds in global average surface temperature. Arrows show the potential interactions among the tipping elements (Source: Steffen et al. (2018)

When representatives of 196 countries negotiated the Paris Agreement in 2015, the goal was that the globe should not exceed an average rise in temperature of 2 degrees in relation to a pre-industrial level. However, according to a new perspective paper from an international research team that includes Professor Katherine Richardson from the DNRF center CMEC, the 2-degree goal is far from enough if global warming is not to escalate.

“We actually do not know whether it is possible to reduce the rise in temperature to a maximum of two degrees as agreed at the Paris summit,” Richardson said. She added:

“Our study suggests that even if possible, the 2-degree rise will already be too much and have pushed the first domino brick, initiating an unstoppable process towards a much warmer climate.”

The comprehensive paper was recently published in the scientific journal Proceedings of the National Academy of Sciences (PNAS) and draws a picture of the need for extensive efforts.

According to Richardson and the rest of the research team, we have already used up one of the two degrees, which is the maximum global temperature rise agreed to in the Paris Agreement. And if the 2-degree rise is reached first, climate events can lead to a serious and uncontrollable domino effect that could cause a so-called “hothouse Earth” state, with a global average temperature rise of 4-5 degrees. Other consequences would be a sea rise of 10-60 meters, glacier reduction, and a thawing of permafrost containing methane.

“Because these are natural processes, they can probably not be stopped once they’ve started. So we need to act now. With climate change, we have shown that humans are able to influence the systems of the Earth. Therefore, we should also be able to influence them in a positive direction. However, it requires that we not only stop greenhouse gas emissions, but also actively increase the Earth’s storage of CO2. That means, in essence, that there is a need for fundamental change in our society,” said Richardson.

The researchers also conclude that humankind’s behavior over the next 10-20 years will have a decisive impact on the climate of the planet for the next 10,000 to 100,000 years.

The study is based on ten climate-changing processes and examines their combined impact on climate, including potential methane emissions due to melting permafrost in Siberia and the effect of melting ice sheets in Greenland.